The nicotinic acetylcholine receptor has served as the model member of a large superfamily of neurotransmitter-gated ion channels. However, the atomic structural details of this receptor and its cousins has escaped study due to the receptors large size and amphipathic nature. Recently, a crystal structure has been solved of an acetylcholine binding protein AChBP that possesses structural similarity to nicotinic receptors, but does not have a domain that conducts ions through the membrane. The biochemical and functional properties of this new protein have not been elucidated. Using fluorescent and electrophysiological techniques, this proposal will seek to determine if the acetylcholine binding protein serves as a functional analog as well as a structural analog of the nicotinic receptor. Fluorescent labels will be used to determine if the AChBP undergoes changes in conformation and functional state in a manner analogous to the nicotinic receptor. In addition, the AChBP will be spliced to the ion-conducting regions of a neurotransmitter-gated ion channel to determine if it is capable of eliciting ionic currents when exposed to agonist. The experiments proposed will determine if the the AchBP provides a model for receptor function as well as its structure, and may provide insights into the shape of the binding site of this large and important receptor family. [unreadable] [unreadable]